From: Carl Hetherington <cth@carlh.net>
Date: Sat, 23 Nov 2019 09:42:16 +0000 (+0100)
Subject: Don't busy-wait when there's nothing to play.
X-Git-Tag: v2.15.40^2~6
X-Git-Url: https://main.carlh.net/gitweb/?p=dcpomatic.git;a=commitdiff_plain;h=89e92b3e7effafd2ca3aa1e9300777f2d2fb6183

Don't busy-wait when there's nothing to play.
---

diff --git a/src/wx/gl_video_view.cc b/src/wx/gl_video_view.cc
index ddae9bb3c..a461939a7 100644
--- a/src/wx/gl_video_view.cc
+++ b/src/wx/gl_video_view.cc
@@ -334,13 +334,17 @@ try
 		}
 		draw (inter_position, inter_size);
 
-		while (time_until_next_frame() < 5) {
+		while (true) {
+			optional<int> n = time_until_next_frame();
+			if (!n || *n > 5) {
+				break;
+			}
 			get_next_frame (true);
 			add_dropped ();
 		}
 
 		boost::this_thread::interruption_point ();
-		dcpomatic_sleep_milliseconds (time_until_next_frame());
+		dcpomatic_sleep_milliseconds (time_until_next_frame().get_value_or(0));
 	}
 
 	/* XXX: leaks _context, but that seems preferable to deleting it here
diff --git a/src/wx/simple_video_view.cc b/src/wx/simple_video_view.cc
index 6eabbc0b0..e349b865c 100644
--- a/src/wx/simple_video_view.cc
+++ b/src/wx/simple_video_view.cc
@@ -159,7 +159,7 @@ SimpleVideoView::timer ()
 	}
 
 	LOG_DEBUG_PLAYER("%1 -> %2; delay %3", next.seconds(), _viewer->time().seconds(), max((next.seconds() - _viewer->time().seconds()) * 1000, 1.0));
-	_timer.Start (time_until_next_frame(), wxTIMER_ONE_SHOT);
+	_timer.Start (time_until_next_frame().get_value_or(0), wxTIMER_ONE_SHOT);
 
 	if (_viewer->butler()) {
 		_viewer->butler()->rethrow ();
diff --git a/src/wx/video_view.cc b/src/wx/video_view.cc
index 7f93f765e..4edc2cd23 100644
--- a/src/wx/video_view.cc
+++ b/src/wx/video_view.cc
@@ -22,8 +22,10 @@
 #include "wx_util.h"
 #include "film_viewer.h"
 #include "lib/butler.h"
+#include <boost/optional.hpp>
 
 using boost::shared_ptr;
+using boost::optional;
 
 VideoView::VideoView (FilmViewer* viewer)
 	: _viewer (viewer)
@@ -89,13 +91,13 @@ VideoView::one_video_frame () const
 	return dcpomatic::DCPTime::from_frames (1, video_frame_rate());
 }
 
-/** @return Time in ms until the next frame is due */
-int
+/** @return Time in ms until the next frame is due, or empty if nothing is due */
+optional<int>
 VideoView::time_until_next_frame () const
 {
 	if (length() == dcpomatic::DCPTime()) {
 		/* There's no content, so this doesn't matter */
-		return 0;
+		return optional<int>();
 	}
 
 	dcpomatic::DCPTime const next = position() + one_video_frame();
diff --git a/src/wx/video_view.h b/src/wx/video_view.h
index ad492bd43..f9e067043 100644
--- a/src/wx/video_view.h
+++ b/src/wx/video_view.h
@@ -107,7 +107,7 @@ public:
 
 protected:
 	bool get_next_frame (bool non_blocking);
-	int time_until_next_frame () const;
+	boost::optional<int> time_until_next_frame () const;
 	dcpomatic::DCPTime one_video_frame () const;
 
 	int video_frame_rate () const {